Bone imaging in sports medicine.S Shikare, AB Samsi, GH Tilve
Department of Nuclear Medicine, Seth G.S. Medical College, Parel, Mumbai.
Increased participation in sports by the general public leads to increase in sports induced injuries including stress fractures, shin splints, arthritis and host of musculotendenous maladies. We have studied twenty patients referred from sports clinic for bone scanning to evaluate clinically difficult problems. It showed stress fracture in twelve patients, bilateral shin splint in five patients and normal bone scan in three patients. Present study highlights the utility of bone imaging for the diagnosis of various sports injuries in sports medicine.
Keywords: Adult, Athletic Injuries, radiography,radionuclide imaging,Diagnosis, Differential, Fractures, Stress, radiography,radionuclide imaging,Human, Tendinitis, radionuclide imaging,Tibia,
In sports medicine stress fracture is probably one of the most common yet serious malady afflicting participants of endurance sports such as distance running. Differentiation from other causes of lower extremity pain such as tendinitis, interosseous membrane tearing, anterior tibial syndrome, anterior tibial tenosy novitis may be very difficult,.
Bone scanning has been displayed successfully for the diagnosis of stress lesion.
A total of twenty patients were studied, age group ranged from 27-35 years with mean age of 31 years. The majority of patients were atheletes, had history of tibial pain ranging from two to six weeks durations.
On examinations majority of patients had tenderness over the shin of tibia (middle/lower 1/3rd). Only three patients had tenderness over lower fibular region.
X-rays of the majority of the patients were normal except in one patient where x-ray showed evidence of stress fracture.
Bone scan of the lower extremity was done three hours following an I/V injection of 740 Mbq of 99Tc MDp and images were taken using general purpose parallel hole collimator with dyna 4 picker gamma camera in anterior and laterally rotated positions.
Bone scan showed focal increase of tracer concentration at the site of stress fracture to superficial peristeal hyperconcentration of tracer in shin splint.
Out of twenty patients twelve patients did show focal increase of tracer concentration involving the tibia (left 3, right 6), while three of the patients showed involvement of lower end of right fibula. X-ray was positive for stress fracture in one patient.
Five patients showed bilateral hyperconcentration of tracer in the region of posteriotibial muscle suggesting shin splint. In all these patients x-rays were normal.
Three patients had normal bone scan and the x-rays, they probably had other related sports injuries besides stress fracture and shin splint.
Subacute or chronic lower extremity pain is very common in endurance atheletes including runners, aerobic dancers etc.
Differentiation of the various possible causes on clinical and radiographic grounds may be very difficult and many entities can occur in runners such as arterial entrapment, chondromalsia patellae, compartment syndromes, tendinitis which will not be demonstrated scintigraphically, so that the bone scan of a patient with one of these entities is expected to be normal, probably above three patients had one of these entities hence may have normal bone scans.
Stress fracture is usually the results of persistent over use of a bone unaccustomed to stress, causing a rapid focal circumferential periosteal resorption with formation of small cortical cavities. Simultaneously, although at a slow rate, denser, stronger, lamellar bone is laid down along lines of stress,. The net effect is a transient weakening of the cortex which may actually reptu with continued stress.
Typically the pain is severe and there may be local heat, swelling, redness. The bone scan usually shows dense focal increased tracer concentration at the site of the fracture. The x-rays are frequently normal.
Prather et al, in a series of 21 patients with stress fracture noted that only six had positive x-rays while all 21 had positive bone scans. They noted sensitivity and specificity for bone scan detection of stress fracture as 100% and 76% and for bone x-rays 26% and 100%.
In our series of twelve patients with stress fracture, bone scan showed sensitivity and specificity of 100% while x-rays showed sensitivity of 8% and specificity of 100%.
Regarding the shin splint there is considerable disagreement in the literature as to the precise definition of shin splint. Some authors believe,, that they represent a form of stress fracture or microfracture while others, feel they donít. The 1968 AMA subcommittee on sports injuries defines shin splint as periostetis or musculotendenous injury not a stress fracture or ischemic disorder.
Shin splint refer to a severe pain along the insertion of muscle into tibia of fibula. Usually the posterior tibial muscle is involved with pain along the mid distal portion of posteriomedial margin of tibia. While the mechanism of injury, the symptoms and to an extent the scintigraphic finding overlap with stress fracture. The two entities are different since the athelete may recover spontaneously from shin splint.
The scintigraphic pattern was described by Libermann and Hemingway as a superficial periosteal hyperconcentration of tracer in shin splint.
This study highlights that bone scanning is highly sensitive in detecting bone stress lesions, in most cases where radigraphs remain normal. No significant difference in the clinical presentation, type or location of lesion were found.
Bone scanning should be performed when the patient has unexplained pain and radigraphs appears normal. Even if a specific diagnosis cannot be made, objective evidence of an osseous abnormality can be obtained and anatomic localisation of stress response can be demonstrated.
We thank the Dean, Seth GS Medical College and KEM Hospital for allowing us to publicise this article.